GAA Nanosheet FET Structure for Threshold Voltage Modulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gate-All-Around (GAA) nanosheet field effect transistors (FETs) face limitations in modulating the threshold voltage (Vt) due to isolation from a substrate bias in fully depleted semiconductor on insulator (FDSOI) technologies.
Innovation Solution
The structure comprises stacked semiconductor nanosheets with gate structures surrounding them, a conductive material between the nanosheets and gate structures, and inner sidewall spacers, allowing for improved back gate biasing and adjustment of Vt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If nanosheet FETs are isolated from substrate bias in FDSOI technologies, then device density and performance are increased, but the ability to modulate Vt is limited
Solution Approach 1:
The gate structure is segmented into multiple independent gates (first gate, second gate, third gate) that can be independently controlled. Each gate can be biased separately to modulate the threshold voltage of the nanosheet channel, enabling fine-grained control while maintaining the isolated nanosheet architecture that provides high device density
Solution Approach 2:
A conductive material is introduced as an intermediary between the nanosheet and the gate structures. This conductive layer enables electrical coupling between the gates and the nanosheet channel, allowing threshold voltage modulation through gate biasing while preserving the physical isolation of the nanosheet from the substrate
2Productivity
If gate structures surround multiple nanosheet channel regions, then device density is increased, but control over threshold voltage modulation is reduced
Solution Approach 1:
The surrounding gate structure is divided into multiple independently controllable gate segments (first gate over first nanosheet, second gate over second nanosheet, third gate over third nanosheet). This segmentation allows each gate to independently modulate the threshold voltage of its corresponding nanosheet channel, maintaining ease of control while achieving high device density through the multi-nanosheet configuration
Solution Approach 2:
The gate structure is designed to be dynamically controllable, with each gate capable of independent biasing. This dynamic control enables flexible adjustment of threshold voltages for different nanosheets, allowing the device to adapt its electrical characteristics for different operating conditions while maintaining the compact multi-nanosheet structure
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to gate-all-around field effect transistors and methods of manufacture. The structure includes: a plurality of stacked semiconductor nanosheets over a semiconductor substrate; a plurality of gate structures surrounding the plurality of semiconductor nanosheets; a conductive material between the plurality of semiconductor nanosheets and the plurality of gate structures; an inner sidewall spacer adjacent to each of the plurality of gate structures and conductive material; and source/drain regions on opposing sides of the plurality of gate structures, separated therefrom by the inner sidewall spacer.